Memory Device with Protection Capability and Method of Accessing Data Therein

ABSTRACT

The present invention is directed to a memory device with protection capability and a method of accessing data therein. A spreader encrypts input user data according to an entered password, and the encrypted data is then stored in a storage area. A despreader performs reverse process of the spreader on the stored data according to the entered password.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a memory device, and moreparticularly to a memory device with protection capability.

2. Description of the Prior Art

Flash memory is a non-volatile storage device that is capable of beingerased and reprogrammed. Moreover, the flash memory generally providesfast data access. Accordingly, the flash memory is widely used in avariety of electronic devices. Owing to technology advance, modern flashmemory devices become denser and more compact. In addition tocompactness of the flash memory, data security is also an importantissue for the flash memory, particularly for a high-volume flash memorythat contains huge amount of data.

Most conventional flash memory devices such as memory sticks have noschemes of protecting the stored data. Even a few modern flash memorydevices provide data protection such as password verification, thestored data itself is not protected and therefore is still at risk ofbeing stolen or destructed.

For the reason that conventional flash memory devices provide noprotective strategies, a need has arisen to propose a novel scheme forprotecting the stored data from being stolen or destructed in a securemanner.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the embodiment of thepresent invention to provide a memory device, such as a flash memorydevice, with effective protection capability and a method of securelyaccessing data in the memory device.

According to the embodiment of the memory device with protectioncapability, a spreader encrypts input user data according to an enteredpassword. A storage area is used for storing encrypted data. Adespreader performs reverse process of the spreader on the stored dataaccording to the entered password.

According to the embodiment of the method of accessing data in a memorydevice with protection capability, user data is inputted to the memorydevice. A password is entered and a storage mode is selected. The userdata is encrypted according to the selected storage mode, and theencrypted data is stored in a storage area. Subsequently, a request toretrieve the stored data is received. A password is secondly entered,and a corresponding storage mode is determined according to the secondlyentered password. The stored data is decrypted by performing a reverseprocess of the encryption. The decrypted data is then retrieved from thememory device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a block diagram of a memory device with protectioncapability according to one embodiment of the present invention;

FIG. 1B shows a block diagram of a memory device with protectioncapability according to an alternative embodiment;

FIG. 2 shows a detailed block diagram of the spreader of FIG. 1A or FIG.1B;

FIG. 3 shows a detailed block diagram of the despreader of FIG. 1A orFIG. 1B;

FIG. 4 shows an exemplary PR code generator of FIG. 2 or FIG. 3;

FIG. 5 shows a flow diagram that illustrates a method of storing data ina memory device with protection capability according to one embodimentof the present invention; and

FIG. 6 shows a flow diagram that illustrates a method of retrieving datafrom a memory device with protection capability according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A shows a block diagram of a memory device with protectioncapability according to one embodiment of the present invention. FIG. 1Bshows an alternative embodiment. Although flash memory is illustrated ineither embodiment, it is appreciated that other types of memory devicemay be adapted as well.

In the embodiment, the memory device includes a spreader 10 and anerror-correcting code (ECC) encoder 12 in a data input path, andincludes a despreader 14 and an ECC decoder 16 in a data output path.Input user data are processed by the spreader 10 and the ECC encoder 12before being stored in a storage area (e.g., flash memory) 18. In theembodiment, the spreader 10 is used to encrypt the input user dataaccording to an entered password, and the ECC encoder 12 is used todetect and correct error(s) in the data. After the stored data of thestorage area 18 are processed by the ECC decoder 16 and the despreader14, the original user data may be recovered. In the embodiment, thedespreader 14 is used to decrypt (i.e., a reverse process of theencryption in the spreader 10) the stored data of the storage area 18,and the ECC decoder 16 is used to perform reverse process of the ECCencoding in the ECC encoder 12. As shown in FIG. 1B, the order of thespreader 10 and the ECC encoder 12 is interchangeable. Similarly, theorder of the ECC decoder 16 and the despreader 14 is alsointerchangeable.

FIG. 2 shows a detailed block diagram of the spreader 10 of FIG. 1A orFIG. 1B. In the embodiment, the spreader 10 primarily includes a seedgenerator 100, a pseudo-random code generator 102 and a logic gate 104such as an exclusive-OR (XOR) gate. Specifically, the seed generator 100generates one or more seeds according to the entered password. Thepseudo-random code generator 102 then generates pseudo-random (PR) codesequence according to the generated seed. A variety of exemplaryembodiments of generating the seed(s) will be described later in thisspecification. The PR code sequence is then XOR-ed with original data(e.g., the input user data (FIG. 1A) or the ECC encoded data (FIG. 1B))by the XOR gate 104, resulting in protected data to be stored in thestorage area 18 (FIG. 1A or FIG. 1B).

FIG. 3 shows a detailed block diagram of the despreader 14 of FIG. 1A orFIG. 1B. In the embodiment, the despreader 14 primarily includes a seedgenerator 140, a pseudo-random code generator 142 and a logic gate 144such as an exclusive-OR (XOR) gate. Specifically, the seed generator 140generates one or more seeds according to the entered password. Thepseudo-random code generator 142 then generates pseudo-random (PR) codesequence according to the generated seed. The PR code sequence is thenXOR-ed with protected data (e.g., the stored data (FIG. 1B) or the ECCdecoded data (FIG. 1A)) by the XOR gate 144, resulting in original datathat are the recovered user data (FIG. 1A) or the data to be ECC decoded(FIG. 1B).

FIG. 4 shows an exemplary PR code generator 102 or 142 of FIG. 2 or FIG.3. A gold code generator is exemplified in this embodiment.Specifically, sequences (a₆a₅a₄a₃a₂a₁a₀) and (a′₆a′₅a′₄a′₃a′₂a′₁a′₀) arethe seeds generated by the seed generator 100 or 140 according to anentered password. In another embodiment, the seeds may be predeterminedsequences. Generally speaking, the gold code generator is constructedbased on the linear feedback shift register (LFSR) structure. As shownin the figure, results of two LFSR branches, e.g., g(D) and g′(D), areoperated by a logic gate such as an XOR gate to generate a gold codeoutput, i.e., the PR code sequence.

FIG. 5 shows a flow diagram that illustrates a method of storing data ina memory device with protection capability according to one embodimentof the present invention. In step 51, user data are inputted to thememory device. In step 52, a user is asked to enter a password and thenselect a storage mode. According to user requirement such as theimportance of the data to be protected, the embodiment may providedifferent storage modes with different protection capability. Forexample, an advanced storage mode may use seed having length longer thanthat in a basic storage mode. Alternatively, the user may skip thepassword asking and directly proceed to store the user data, in a normalmode, without protection. Subsequently, in step 53, the user data arethen encrypted and ECC encoded according to the selected storage mode,if the password is successfully verified. It is noted that, in someembodiment, the ECC encoding may still be performed even the normal modeis selected. Finally, in step 54, the encrypted/ECC encoded data arestored in a storage area such as the flash memory.

FIG. 6 shows a flow diagram that illustrates a method of retrieving datafrom a memory device with protection capability according to oneembodiment of the present invention. In step 61, the memory devicereceives a request (from a user) to retrieve data. In step 62, the useris asked to enter a password. A corresponding storage mode is determinedaccording to the entered password. Alternatively, the user may skip thepassword asking and directly proceed to retrieve unprotected data in anormal mode. Subsequently, in step 63, the stored data are thendecrypted and ECC decoded according to the selected storage mode, if thepassword is successfully verified. It is noted that, in some embodiment,the ECC decoding may still be performed even the normal mode isselected. Finally, in step 64, the decrypted/ECC decoded data areretrieved from the memory device.

Some exemplary methods of generating the seeds are demonstrated in thefollowing exemplary embodiments.

Exemplary Embodiment I

with respect to a basic storage mode, the entered password istransformed from a decimal form to a binary form. For example, apassword 7849 is transformed to (13-bit) “1111010101001”. In order toobtain 14-bit seed sequence required by the PR code generator (e.g.,gold code generator) shown in FIG. 4, the 13-bit password is duplicatedto result in 26-bit sequence, i.e., “1111010101001 1111010101001”. Thefirst 14 bits of the 26-bit sequence is then used as the seed for the PRcode generator.

With respect to an advanced storage mode, a seed with twofold length(i.e., 28-bit seed) is required for increasing the protectioncapability. Accordingly, the 13-bit password is duplicated twice toresult in 39-bit sequence, i.e., “1111010101001 11110101010011111010101001”. The first 28 bits of the 39-bit sequence is then used asthe seed for the PR code generator.

Exemplary Embodiment II

With respect to a basic storage mode, the entered password istransformed from a decimal form to a binary form, and is then processedby Hash algorithm such as SHA-1, SHA-256 or SHA-512. For example, apassword 6382179 is transformed to (24-bit) “01100001 0110001001100011”. The (24-bit) binary sequence is processed by SHA-512 toresult in 512-bit message digest, which may be expressed in hexadecimalform as ddaf35a193617aba cc417349ae204131 12e6fa4e89a97ea20a9eeee64b55d39a 2192992a274fc1a8 36ba3c23a3feebbd 454d4423643ce80e2a9ac94fa54ca49f”. The first 14 bits of the 512-bit sequence is thenused as the seed for the PR code generator.

With respect to an advanced storage mode, a seed with twofold length(i.e., 28-bit seed) is required for increasing the protectioncapability. Accordingly, the first 28 bits of the 512-bit sequence isthen used as the seed for the PR code generator.

Exemplary Embodiment III

The 512-bit sequence regenerated by SHA-512 in the previous exemplaryembodiment is duplicated to result in 1024-bit sequence of “0” and “1”.Each bit of the 1024-bit is associated with a data block. In thisexemplary embodiment, the data block associated with the bit “1” isencrypted/encoded, while the data block associated with the bit “0” isleft un-encrypted and en-encoded.

Although specific embodiments have been illustrated and described, itwill be appreciated by those skilled in the art that variousmodifications may be made without departing from the scope of thepresent invention, which is intended to be limited solely by theappended claims.

1. A memory device with protection capability, comprising: a spreaderfor encrypting input user data according to an entered password; astorage area for storing encrypted data; and a despreader for performingreverse process of the spreader on the stored data according to theentered password.
 2. The memory device of claim 1, further comprising:an error-correcting code (ECC) encoder for detecting and correctingerror of the input user data or the encrypted data.
 3. The memory deviceof claim 2, further comprising: an error-correcting code (ECC) decoderfor performing reverse process of the ECC encoder on the stored data. 4.The memory device of claim 1, wherein the storage area comprises flashmemory.
 5. The memory device of claim 1, wherein the spreader comprises:a seed generator for generating at least one seed according to theentered password; a pseudo-random (PR) code generator for generating aPR code sequence according to the seed; and a logic gate for operatingon original data inputting to the spreader and the PR code sequence,therefore resulting in protected data to be stored in the storage area.6. The memory device of claim 5, wherein the logic gate comprises anexclusive-OR gate.
 7. The memory device of claim 5, wherein the PR codegenerator comprises a gold code generator.
 8. The memory device of claim5, wherein the seed is generated by taking a portion of binary bits ofthe entered password.
 9. The memory device of claim 8, wherein thebinary bits of the entered password are further duplicated.
 10. Thememory device of claim 5, wherein the seed is generated by subjectingbinary bits of the entered password to Hash operation, followed bytaking a portion of binary bits of the Hash-operated password.
 11. Thememory device of claim 10, wherein the binary bits of the Hash-operatedpassword are further duplicated.
 12. The memory device of claim 11,wherein each binary bit of the duplicated Hash-operated password isassociated with a data block, and the encryption and decryption of thedata block is performed according to the binary bit “0” or “1”.
 13. Thememory device of claim 1, wherein the despreader comprises: a seedgenerator for generating at least one seed according to the enteredpassword; a pseudo-random (PR) code generator for generating a PR codesequence according to the seed; and a logic gate for operating onprotected data inputting to the despreader and the PR code sequence,therefore resulting in recovered data to be retrieved from the memorydevice.
 14. The memory device of claim 13, wherein the logic gatecomprises an exclusive-OR gate.
 15. The memory device of claim 13,wherein the PR code generator comprises a gold code generator.
 16. Amethod of accessing data in a memory device with protection capability,comprising: inputting user data to the memory device; after a passwordis entered and a storage mode is selected, encrypting the user dataaccording to the selected storage mode; and storing the encrypted datain a storage area.
 17. The method of claim 16, further comprising a stepof: error-correcting the input user data or the encrypted data.
 18. Themethod of claim 17, further comprising a step of: performing reverseprocess of the error-correcting on the stored data.
 19. The method ofclaim 16, wherein the storage area comprises flash memory.
 20. Themethod of claim 16, further comprising steps of: receiving a request toretrieve the stored data; after a password is secondly entered,determining a corresponding storage mode according to the secondlyentered password; decrypting the stored data by performing a reverseprocess of the encryption; and retrieving the decrypted data from thememory device.
 21. The method of claim 16, wherein the encryption stepcomprises: generating at least one seed according to the enteredpassword; generating a pseudo-random (PR) code sequence according to theseed; and logically operating on input original data and the PR codesequence, therefore resulting in protected data to be stored in thestorage area.
 22. The method of claim 20, wherein the decryption stepcomprises: generating at least one seed according to the secondlyentered password; generating a PR code sequence according to the seed;and logically operating on input protected data and the PR codesequence, therefore resulting in recovered data to be retrieved from thememory device.